Distribution: N - VG, Frl, Ven (Thor & Nascimbene 2007), Lig. C - Tosc (Tretiach & al. 2008), Marc (Nimis & Tretiach 1999), Abr (Nimis & Tretiach 1999, Gheza & al. 2021). S - Camp (Ricciardi & al. 2000), Pugl (Nimis & Tretiach 1999), Bas (Potenza & al. 2014), Cal (Puntillo 1996).
Description: Thallus crustose, finely granular, entirely made of 20-40 µm wide, green goniocysts that may or may not form coralline structures. Apothecia biatorine, 0.3-0.7(-1.3) mm across, whith a white-grey to grey-brown disc, often with a slight violet hue, and a paler, raised, sometimes white-pruinose proper margin. Proper exciple without crystals, the rim colourless to pale brown, the hyphae towards the outer part with ellipsoidal lumina, 3-7 x 1.5-5 μm; hymenium colourless or pale brown in upper part; paraphyses 1-1.6 µm thick at mid-level, the apical cells clavate to slightly thickened, up to 4 µm wide; hypothecium and adjacent excipulum dark brown to red-brown K+ dark brown (Arnoldiana-brown pigment). Asci 8-spored, cylindrical-clavate, approaching the Bacidia-type, but the ocular chamber wider, and the axial body never penetrating through the entire d-layer, surrounded by a narrow, darker amyloid layer. Ascospores 1-3(-7)-septate, hyaline, acicular, straight to curved, (19-)24-48 x 0.9-2 µm. Pycnidia white, abundant or rare, 0.1-0.2 mm diam. Conidia filiform, arched or curved, sometimes almost straight, without any hook at apex, 0-3(-5)-septate, 25-40 x 1-1.5 μm.. Photobiont chlorococcoid. Spot tests: Thallus K-, C-, KC-, P-, UV-. Chemistry: thallus without lichen substances; Arnoldiana-brown pigment in apothecia.
Note: a mild-temperate lichen found on more or less calciferous rocks in sheltered situations, especially in open woodlands; often sterile, and much overlooked. Some epiphytic records could refer to B. sulphurella.
Growth form: Crustose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by soredia, or soredia-like structures (e.g. blastidia)
Most common in areas with a humid-warm climate (e.g. most of Tyrrenian Italy)